1. Field of the Invention
The present invention relates to a fundus oculi observation device and an ophthalmic image display device that are used for observation of a fundus oculi of an eye.
2. Description of the Related Art
As a fundus oculi observation device, a retinal camera has been widely used conventionally. FIG. 15 shows an example of the appearance of a conventional and general retinal camera. FIG. 16 shows an example of the configuration of an optical system internally accommodated in the retinal camera (refer to Japanese Unexamined Patent Application Publication JP-A 2004-350849, for example). First, referring to FIG. 15, the appearance of a conventional retinal camera 1000 will be described. The retinal camera 1000 is provided with a platform 3 mounted on a base 2 so as to be slidable in the front and rear, right and left directions (horizontal directions). On this platform 3, an operation panel and a control lever 4 for an examiner to perform various operations are mounted.
The examiner can 3-dimensionally move the platform 3 on the base 2 by operating the control lever 4. On the top of the control lever 4, an operation button 4a pressed down at the time of capturing a fundus oculi is mounted.
On the base 2, a post 5 is mounted standing upward. This post 5 is provided with a jaw rest 6 where a jaw of a subject is rested, and an external fixation lamp 7 serving as a light source for fixing an eye E.
On the platform 3, a main body part 8 is placed for accommodating various optical systems and control systems of the retinal camera 1000. The control system may be placed, for example, inside the base 2 or the platform 3, or in an external device such as a computer connected to the retinal camera 1000.
On the eye E side of the main body part 8 (i.e., on the left side on the sheet of FIG. 15), an objective lens part 8a placed facing the eye E is disposed. Moreover, on the examiner's side (i.e., on the right side on the sheet of FIG. 15), an eyepiece part 8b for observing the fundus oculi of the eye E with naked eyes is disposed.
Furthermore, to the main body part 8, a still camera 9 for producing a still image of the fundus oculi of the eye E and an imaging device 10 such as a TV camera for producing a still image or moving image of the fundus oculi are disposed. The still camera 9 and the imaging device 10 are formed so as to be removable from the main body part 8.
As the still camera 9, in accordance with various conditions such as the purpose of an examination and a method of saving a captured image, a digital camera equipped with an imaging device such as a CCD (charge coupled device) and a CMOS (complementary metal oxide semiconductor), a film camera, an instant camera and the like may be interchangeably used as necessary. The main body part 8 is provided with a mounting part 8c for interchangeably mounting the still camera 9.
In a case where the still camera 9 and the imaging device 10 are of digital imaging type, it is possible to send image data of fundus oculi images captured by these components to a computer or the like connected to the retinal camera 1000, and observe by displaying the fundus oculi images on a display. Further, it is possible to send the image data to an image recording device connected to the retinal camera 1000 and create a database, and use it as, for example, electronic data for creating an electronic medical record.
Further, on the examiner's side of the main body part 8, a touch panel monitor 11 is disposed. On this touch panel monitor 11, a fundus oculi image of the eye E formed based on video signals outputted from the (digital-type) still camera 9 or imaging device 10 is displayed. Moreover, on the touch panel monitor 11, an x-y coordinate system taking the center of a screen as the origin is displayed superimposed on the fundus oculi image. When the examiner touches the screen, coordinate values corresponding to a touched position are displayed.
Next, referring to FIG. 16, the configuration of the optical system of the retinal camera 1000 will be described. The retinal camera 1000 is provided with an illumination optical system 100 that illuminates a fundus oculi Ef of the eye E, and an imaging optical system 120 that guides the illumination light reflected by the fundus oculi to the eyepiece part 8b, the still camera 9 and the imaging device 10.
The illumination optical system 100 comprises: an observation light source 101; a condenser lens 102; an imaging light source 103; a condenser lens 104; exciter filters 105 and 106; a ring transparent plate 107; a mirror 108; an LCD (Liquid Crystal Display) 109; an illumination diaphragm 110; a relay lens 111; an aperture mirror 112; and an objective lens 113.
The observation light source 101 is composed of, for example, a halogen lamp, and emits continuous light for fundus oculi observation. The condenser lens 102 is an optical element for converging the continuous light (observation illumination light) emitted by the observation light source 101 and almost evenly applying the observation illumination light to the fundus oculi Ef.
The imaging light source 103 is composed of, for example, a xenon lamp, and is flashed at the time of imaging of the fundus oculi Ef. The condenser lens 104 is an optical element for converging the flash light (imaging illumination light) emitted by the imaging light source 103 and evenly applying the imaging illumination light to the fundus oculi Ef.
The exciter filters 105 and 106 are filters used at the time of fluorography of an image of the fundus oculi Ef. The exciter filters 105 and 106 can be respectively inserted into and removed from an optical path by a drive mechanism (not illustrated) such as a solenoid. The exciter filter 105 is placed on the optical path at the time of FAG (fluorescein angiography). The exciter filter 106 is placed on the optical path at the time of ICG (indocyanine green angiography). At the time of color-imaging, both the exciter filters 105 and 106 are retracted from the optical path.
The ring transparent plate 107 is placed in a conjugating position with a pupil of the eye E, and is provided with a ring transparent part 107a taking the optical axis of the illumination optical system 100 as the center. The mirror 108 reflects the illumination light emitted by the observation light source 101 or imaging light source 103, in a direction of the optical axis of the imaging optical system 120. The LCD 109 displays a fixation target (not illustrated) for fixing the eye E.
The illumination diaphragm 110 is a diaphragm member to shut out part of the illumination light in order to prevent flare and the like. This illumination diaphragm 110 is configured so as to be movable in the optical axis direction of the illumination optical system 100, and is thus capable of changing an illumination region of the fundus oculi Ef.
The aperture mirror 112 is an optical element that combines the optical axis of the illumination optical system 100 and the optical axis of the imaging optical system 120. In the center region of the aperture mirror 112, an aperture 112a is opened. The optical axis of the illumination optical system 100 and the optical axis of the imaging optical system 120 cross each other at a substantially central position of the aperture 112a. The objective lens 113 is installed in the objective lens part 8a of the main body part 8.
The illumination optical system 100 having such a configuration illuminates the fundus oculi Ef in the following manner. First, at the time of fundus oculi observation, the observation light source 101 is turned on and an observation illumination light is emitted. This observation illumination light is applied to the ring transparent plate 107 through the condenser lenses 102 and 104 (the exciter filters 105 and 106 are retracted from the optical path). The light passed through the ring transparent part 107a of the ring transparent plate 107 is reflected by the mirror 108 and, after passing through the LCD 109, the illumination diaphragm 110 and the relay lens 111, is reflected by the aperture mirror 112. The observation illumination light reflected by the aperture mirror 112 travels in the optical axis direction of the imaging optical system 120, and is converged by the objective lens 113, thereby entering the eye E and illuminate the fundus oculi Ef.
At this moment, since the ring transparent plate 107 is placed in a conjugating position with the pupil of the eye E, a ring-shaped image of the observation illumination light entering the eye E is formed on the pupil. The entering fundus oculi reflection light of the entered observation illumination light is emitted from the eye E through a central dark part of the ring-shaped image on the pupil. Thus, the observation illumination light entering the eye E is prevented from affecting the fundus oculi reflection light of the observation illumination light.
On the other hand, at the time of imaging of the fundus oculi Ef, flush light is emitted from the imaging light source 103, and the imaging illumination light is applied to the fundus oculi Ef through the same path. In the case of fluorography, either the exciter filter 105 or the exciter filter 106 is selectively placed on the optical path, depending on whether FAG imaging or ICG imaging is carried out.
Next, the imaging optical system 120 will be described. The imaging optical system 120 comprises: an objective lens 113; an aperture mirror 112 (an aperture 112a thereof); an imaging diaphragm 121; barrier filters 122 and 123; a variable magnifying lens 124; a relay lens 125; an imaging lens 126; a quick return mirror 127; and an imaging media 9a. Herein, the imaging media 9a is an imaging media (a CCD, camera film, instant film or the like) for the still camera 9.
The fundus oculi reflection light of the illumination light exiting from the eye E through the central dark part of the ring-shaped image formed on the pupil enters the imaging diaphragm 121 through the aperture 112a of the aperture mirror 112. The aperture mirror 112 reflects cornea reflection light of the illumination light, and acts so as not to mix the cornea reflection light into the fundus oculi reflection light entering the imaging diaphragm 121. Consequently, generation of flare in observation images and captured images is inhibited.
The imaging diaphragm 121 is a plate-shaped member having a plurality of circular light-transmitting parts of different sizes. The plurality of light-transmitting parts compose diaphragms with different diaphragm values (F values), and are placed alternatively on the optical path by a drive mechanism (not illustrated).
The barrier filters 122 and 123 can be inserted into and removed from the optical path by a drive mechanism (not illustrated) such as a solenoid. In FAG imaging, the barrier filter 122 is placed on the optical path, whereas in ICG imaging, the barrier filter 123 is placed on the optical path. Further, at the time of color-imaging, both the barrier filters 122 and 123 are retracted from the optical path.
The variable magnifying lens 124 is movable in the optical axis direction of the imaging optical system 120 by a drive mechanism (not illustrated). This makes it possible to change an observation magnifying ratio and an imaging magnifying ratio, and to focus images of the fundus oculi. The imaging lens 126 is a lens that focuses the fundus oculi reflection light from the eye E onto the imaging media 9a. 
The quick return mirror 127 is disposed so as to be capable of being rotated around a rotary shaft 127a by a drive mechanism (not illustrated). In a case where imaging of the fundus oculi Ef is performed with the still camera 9, the fundus oculi reflection light is guided to the imaging media 9a by springing up the quick return mirror 127 that is obliquely mounted on the optical path. Meanwhile, in a case where imaging of the fundus oculi is performed with the imaging device 10, or in a case where observation of the fundus oculi is performed with the naked eye of the examiner, the quick return mirror 127 is obliquely mounted on the optical path to upwardly reflect the fundus oculi reflection light.
The imaging optical system 120 is further provided with, for guiding the fundus oculi reflection light reflected by the quick return mirror 127, a field lens 128, a switching mirror 129, an eyepiece 130, a relay lens 131, a reflection mirror 132, an imaging lens 133, and an image pick-up element 10a. The image pick-up element 10a is an image pick-up element such as a CCD installed in the imaging device 10. On the touch panel monitor 11, a fundus oculi image Ef imaged by the image pick-up element 10a is displayed.
The switching mirror 129 is rotatable around a rotary shaft 129a in the same manner as the quick return mirror 127. This switching mirror 129 is obliquely disposed on the optical path during observation with the naked eye, thereby reflecting and guiding the fundus oculi reflection light to the eyepiece 130.
Further, at the time of capture of a fundus oculi image by using the imaging device 10, the switching mirror 129 is retracted from the optical path, and the fundus oculi reflection light is guided toward the image pick-up element 10a. In this case, the fundus oculi reflection light is passed through the relay lens 131 and reflected by the mirror 132, whereby an image is formed in the image pick-up element 10a by the imaging lens 133.
This retinal camera 1000 is a fundus oculi observation device used for observing the state of the surface of the fundus oculi Ef, namely, the state of the retina. In other words, the retinal camera 1000 is a device for acquiring a 2-dimensional fundus oculi image when the fundus oculi Ef is seen from the cornea of the eye E. On the other hand, organs such as the choroidea and the sclera exist in the deeper layers of the retina. There has been a demand for a technique for observing the state of these organs, and in recent years, there has been progress in the practical utilization of devices for observing these deeper layer organs (refer to Japanese Unexamined Patent Application Publications Nos. JP-A 2003-000543 and JP-A 2005-241464).
Each of the devices disclosed in JP-A 2003-000543 and JP-A 2005-241464 is an optical image measurement device to which a so-called OCT (Optical Coherence Tomography) technology is applied (referred to as an optical coherence topography device, or the like). Such an optical image measurement device is a device that splits low-coherence light into two, guides one (signal light) of the lights to the fundus oculi and the other (reference light) to a given reference object, and detects and analyzes interference light obtained by superimposing the signal light passed through the fundus oculi and the reference light reflected by the reference object, thereby forming tomographic images of the surface and deep layer tissue of the fundus oculi or 3-dimensional images of the fundus oculi. Here, the optical image measurement device disclosed in JP-A 2003-000543 is generally called a Fourier domain OCT or the like.
The Fourier domain OCT is configured to scan with a signal light and apply the signal light to a fundus oculi, thereby forming a tomographic image having a depth-wise cross section along a scanning line. Such scan with a signal light is referred to as B-scan or the like (refer to, for example, NEDO Workshop “Seeing (examining) inside the body from the ‘window’ of the human body, the fundus oculi”—Development of an ultra early diagnostic device for lifestyle-related diseases using the latest optical technologies (held on Apr. 25, 2005), Internet <URL:http://www.nedo.go.jp/informations/koubo/170627—2/besshi3.pdf>).
Further, in the case of formation of a 3-dimensional image of a fundus oculi, 3-dimensional image data is generated by executing B-scan along a plurality of scanning lines and subjecting the plurality of tomographic images obtained thereby to an interpolation process. This 3-dimensional image data is referred to as volume data, voxel data or the like as in a medical image diagnosis device such as an X-ray CT device, and is image data with a form in which pixel data (data of brightness, contrasting density, color, etc., including a luminance value and a RGB value) is assigned to each of voxels arranged 3-dimensionally. The 3-dimensional image is displayed as a pseudo 3-dimensional image taken on a specific view direction obtained by rendering the volume data. In this specification, an image acquired by the optical image measurement device may be referred to as an OCT image.
In order to grasp the state (presence or absence of a disease) of a fundus oculi in detail, it is desirable to consider both an image acquired by a retinal camera and an image acquired by an optical image measurement device. This is because it is difficult to grasp the state of a deep layer organ such as choroidea and sclera in detail from only an image of a fundus oculi surface acquired by a retinal camera and it is hard to grasp the state of the fundus oculi surface throughout a wide range in detail from observation of only a fundus oculi image acquired by an optical image measurement device.
Further, in order to comprehensively determine the state of a fundus oculi, it is important to determine the disease state in consideration of both the state of the fundus oculi surface and the state of the deeper layer organs. In other words, to enhance the accuracy of determination of the disease state, it is desirable that more information is available as a reference, and it is also desirable that the reference information is available from multidimensional angles.
For this purpose, it is necessary to use a fundus oculi observation device that is capable of acquiring a fundus oculi image by a retinal camera and a fundus oculi image by an optical image measurement device. In particular, it is expected that a more detailed diagnosis can be achieved because it is possible, by using a device that is capable of capturing both the fundus oculi images simultaneously, to observe the state of the fundus oculi with one of the fundus oculi images during capture of the other fundus oculi image.
In the case of displaying images by both a retinal camera and an optical image measurement device, it is desirable to show such information that makes it possible to grasp the positional relationship between both the images. As this information, for example, an image showing a measurement range (measurement range image) of an OCT image on a fundus oculi image by a retinal camera will be usable. As the measurement range image, it is possible to use an image showing a range with a specific size (for example, an image like a frame surrounding a range of several mm×several mm approximately).
In the case of displaying such a measurement range image, it is necessary, in order to show the positional relationship between both the images with high accuracy, to match the display sizes of the fundus oculi image and the measurement range image in accordance with the characteristic of each eye.
The characteristic of an eye affecting the display size is, for example, an axial length. Each eye has an individual axial length. For example, an eye of axial myopia has a longer axial length than a healthy eye, and an eye of axial hyperopia has a shorter axial length than a healthy eye.
In a conventional fundus oculi observation device, it is impossible to match the display sizes of a fundus oculi image and a measurement range image, and it is impossible to show the positional relationship between an image by a retinal camera and an OCT image with high accuracy.